The present invention generally relates to flexible containers for housing liquid products. More particularly, the present invention relates to multi-chamber containers having a selectively openable seal line between two chambers.
Flexible containers, constructed from plastic films, are commonly used in the medical field for containing, inter alia, parenteral, enteral, and dialysis solutions. A great variety of such solutions can be housed and stored in such containers.
There are, however, a number of products that due to stability, compatibility, or other concerns must be stored in component parts in separate containers and admixed before use. For example, amino acid and dextrose solutions require separate storage containers or compartments. These components, therefore, are stored separately and then mixed prior to use.
One of the disadvantages of storing components in separate containers and then mixing them together is that the mixing process can compromise sterility of the system. Additionally, this step creates a labor intense process.
To deal with the disadvantages of separate containers, it is known to provide multiple chamber containers having an interior including two or more chambers. One way to create such a container is with a heat seal dividing the interior into two chambers. Such containers are disclosed, for example, in U.S. Pat. Nos. 4,396,388; 4,770,295; 3,950,158; 4,000,996; and 4,226,330.
It is known to use frangible valves between the heat seal to allow for selective communication and mixing of the two components stored in the separate chambers. See, for example, U.S. Pat. No. 4,396,488.
However, such a structurexe2x80x94frangible valvesxe2x80x94may not be desirable for a number of reasons, including, inter alia, cost. An alternative to frangible valves is disclosed in U.S. Pat. Nos. 3,950,158, 4,000,996 and 4,226,330, where multiple chamber containers are disclosed with a line of weakness, such as a score line, which breaks upon the application of pressure.
In U.S. Pat. No. 4,770,295, a selectively openable seal line is positioned between two sheets of flexible thermoplastic material. The seal line is resistant to unintentional opening forces, but opens upon application of a specific force. The seal line may be employed in various containers, including a two chamber container for the separate storage and selective mixing of two medical substances. The container includes two sheets forming the exterior of the container and an inner diaphragm sheet between the outer sheets. One selectively openable seal is disposed between one of the outer sheets and the diaphragm sheet. A permanent line of securement is preferably included between the exterior sheet and the diaphragm sheet extending substantially parallel to and co-extensive with the openable seal line.
In addition, tear tabs or tear strips for plastic packaging are also known, such as shown in U.S. Pat. No. 2,991,000. Such tear tabs provide access to the contents of the container. However, a disadvantage with these containers is that they also involve the use of relatively complicated seal structures. U.S. Pat No. 3,983,994 discloses a seal broken by pulling upon tabs located outside of the container.
Another issue that must be considered in constructing containers for the medical industry is that the solutions, and therefore the containers, often require sterilization after manufacture of the container and solution. Typically, the products are sterilized by steam sterilization, or autoclaving. Autoclave sterilization can alter the thermal properties of the film used to form the container and seal between chambers of the container.
Of course, it is desirable to provide a multi-chamber container with a seal between the chambers that is capable of withstanding external stresses. Such stresses include pressure that may be applied to one or more of the chambers from, for example, squeezing thereof, or accidental dropping of the bag. Therefore, the seal must be sufficiently strong.
However, a difficulty in creating the seal is that the strength of the seal typically increases during sterilization. As a result, a seal may be too strong after the sterilization process making it difficult to separate the seal to combine the components within the chambers.
A need, therefore, exists for a flexible container having chambers separated by a frangible or separable seal that overcomes the disadvantages of the prior art.
The present invention provides a flexible container defining a plurality of internal compartments separated by a seal. At least the seal region is constructed from a film that comprises at least two layers, one of which is RF-responsive and the other layer, the inner layer, being non-RF responsive. The RF-responsive layer, in response to RF energy, heats the non-RF responsive interior layer to form a peelable seal that is defined by a bonding between the non-RF responsive layers that define an interior of the container.
Preferably, the non-RF responsive layer is an alloy of at least two materials that have differing melting points. To create the seal, the layer is heated to a temperature wherein only one of the materials melts.
In an embodiment, the seal layer is an alloy of styrene-ethylene-butyl-styrene (SEBS) and ethylene propylene copolymer. Accordingly, when the seal is being created, the inner layer is heated by the RF-responsive layer to a temperature wherein the SEBS melts and flows into a corresponding inner layer. However, the temperature is not great enough to cause the ethylene propylene copolymer to melt. A seal is created between the two inner layers due to the melting of the SEBS. This creates a strong seal between the two inner layers that can be xe2x80x9cpeeledxe2x80x9d when desired using a force normal thereto.
The present invention also provides a method for making a multi-chamber container comprising the steps of providing a web of plastic film having a first non-RF responsive layer and a second RF-responsive layer; sealing opposing edges of the web of film to create an interior defined, at least in part, by the inner layers; and creating an inner seal, defining at least two chambers, by applying RF energy and causing a portion of the inner layers to seal to themselves.
An advantage of the present invention is to provide a container having a peelable seal capable of withstanding external stresses due to pressure applied to the container or to individual chambers of the container.
A further advantage of the present invention is to provide a container having a peelable seal that strengthens during sterilization yet is capable of being easily opened by healthcare personnel.
Moreover, an advantage of the present invention is to provide a container having a peelable seal which is uniform in strength across the length of the seal allowing for improved performance since the concentration of stress is inside the seal area.
A still further advantage of the present invention is to provide a container having a peelable seal that readily separates when desired.
Another advantage of the present invention is to provide a container having a peelable seal that is RF sealed rather than heat sealed.
A further advantage of the present invention is to provide a container having a peelable seal which is formed with a seal bar that results in a strong, consistent seal.
A still further advantage of the present invention is to provide a container having a peelable seal separating chambers of the container thereby requiring no special polymer alloys, intermediate zones or external devices in order to maintain a separation of solutions.
Moreover, another advantage of the present invention is to provide a container having a peelable seal which stretches when selectively opened rather than fractures.
Yet another advantage of the present invention is to provide a container having a peelable seal which is simple to manufacture using a minimal amount of material.
Another advantage of the present invention is to provide a container in which the solutions and/or products contained therein do not react with the film of the container.